Use minimal javascript expression for bound signals

Previously, QQmlBoundSignal used QQmlExpression internally.  This
commit adds a new, more optimal QQmlJavaScriptExpression subclass
specifically designed for QQmlBoundSignal, and converts the code
to use it instead of QQmlExpression where appropriate.

Task-number: QTBUG-24460
Change-Id: I2865a119ce840235e27a7722d8052ca61c265f69
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>

17 files changed, 358 insertions, 161 deletions

diff --git a/src/qml/debugger/qqmlenginedebugservice.cpp b/src/qml/debugger/qqmlenginedebugservice.cpp
index 2dbabdbf56..4ae956a14f 100644
--- a/src/qml/debugger/qqmlenginedebugservice.cpp
+++ b/src/qml/debugger/qqmlenginedebugservice.cpp
@@ -264,7 +264,7 @@ void QQmlEngineDebugService::buildObjectDump(QDataStream &message,
             QQmlObjectProperty prop;
             prop.type = QQmlObjectProperty::SignalProperty;
             prop.hasNotifySignal = false;
-            QQmlExpression *expr = signalHandler->expression();
+            QQmlBoundSignalExpression *expr = signalHandler->expression();
             if (expr) {
                 prop.value = expr->expression();
                 QObject *scope = expr->scopeObject();
@@ -605,9 +605,9 @@ bool QQmlEngineDebugService::setBinding(int objectId,
                 if (isLiteralValue) {
                     property.write(expression);
                 } else if (hasValidSignal(object, propertyName)) {
-                    QQmlExpression *qmlExpression = new QQmlExpression(context, object, expression.toString());
+                    QQmlBoundSignalExpression *qmlExpression = new QQmlBoundSignalExpression(QQmlContextData::get(context), object, expression.toString(),
+                                                                                             false, filename, line, column);
                     QQmlPropertyPrivate::setSignalExpression(property, qmlExpression);
-                    qmlExpression->setSourceLocation(filename, line, column);
                 } else if (property.isProperty()) {
                     QQmlBinding *binding = new QQmlBinding(expression.toString(), false, object, QQmlContextData::get(context), filename, line, column);;
                     binding->setTarget(property);
diff --git a/src/qml/debugger/qqmlprofilerservice_p.h b/src/qml/debugger/qqmlprofilerservice_p.h
index 20376433f0..a9882463d4 100644
--- a/src/qml/debugger/qqmlprofilerservice_p.h
+++ b/src/qml/debugger/qqmlprofilerservice_p.h
@@ -54,7 +54,7 @@
 //
 
 #include <private/qqmldebugservice_p.h>
-#include "qqmlexpression.h"
+#include <private/qqmlboundsignal_p.h>
 
 #include <QtCore/qelapsedtimer.h>
 #include <QtCore/qmetaobject.h>
@@ -201,7 +201,7 @@ struct QQmlBindingProfiler {
 };
 
 struct QQmlHandlingSignalProfiler {
-    QQmlHandlingSignalProfiler(const QMetaMethod &signal, QQmlExpression *expression)
+    QQmlHandlingSignalProfiler(const QMetaMethod &signal, QQmlBoundSignalExpression *expression)
     {
         enabled = QQmlProfilerService::instance
                 ? QQmlProfilerService::instance->profilingEnabled() : false;
@@ -209,7 +209,7 @@ struct QQmlHandlingSignalProfiler {
             init(signal, expression);
     }
 
-    QQmlHandlingSignalProfiler(QObject *object, int index, QQmlExpression *expression)
+    QQmlHandlingSignalProfiler(QObject *object, int index, QQmlBoundSignalExpression *expression)
     {
         enabled = QQmlProfilerService::instance
                 ? QQmlProfilerService::instance->profilingEnabled() : false;
@@ -226,7 +226,7 @@ struct QQmlHandlingSignalProfiler {
     bool enabled;
 
 private:
-    void init(const QMetaMethod &signal, QQmlExpression *expression)
+    void init(const QMetaMethod &signal, QQmlBoundSignalExpression *expression)
     {
         QQmlProfilerService *service = QQmlProfilerService::instance;
         service->startRange(QQmlProfilerService::HandlingSignal);
diff --git a/src/qml/qml/qqmlabstractexpression_p.h b/src/qml/qml/qqmlabstractexpression_p.h
index fe2ee1762b..1d5ecac08e 100644
--- a/src/qml/qml/qqmlabstractexpression_p.h
+++ b/src/qml/qml/qqmlabstractexpression_p.h
@@ -59,7 +59,7 @@
 
 QT_BEGIN_NAMESPACE
 
-class QQmlAbstractExpression
+class Q_QML_PRIVATE_EXPORT QQmlAbstractExpression
 {
 public:
     QQmlAbstractExpression();
diff --git a/src/qml/qml/qqmlboundsignal.cpp b/src/qml/qml/qqmlboundsignal.cpp
index b375a70d50..446bad855a 100644
--- a/src/qml/qml/qqmlboundsignal.cpp
+++ b/src/qml/qml/qqmlboundsignal.cpp
@@ -49,6 +49,7 @@
 #include "qqml.h"
 #include "qqmlcontext.h"
 #include "qqmlglobal_p.h"
+#include "qqmlrewrite_p.h"
 #include <private/qqmlprofilerservice_p.h>
 #include <private/qv8debugservice_p.h>
 
@@ -59,6 +60,105 @@ Q_DECLARE_METATYPE(QJSValue)
 
 QT_BEGIN_NAMESPACE
 
+static QQmlJavaScriptExpression::VTable QQmlBoundSignalExpression_jsvtable = {
+    QQmlBoundSignalExpression::expressionIdentifier,
+    QQmlBoundSignalExpression::expressionChanged
+};
+
+QQmlBoundSignalExpression::QQmlBoundSignalExpression(QQmlContextData *ctxt, QObject *scope, const QByteArray &expression,
+                                                     bool isRewritten, const QString &fileName, int line, int column)
+    : QQmlJavaScriptExpression(&QQmlBoundSignalExpression_jsvtable)
+{
+    setNotifyOnValueChanged(false);
+    setContext(ctxt);
+    setScopeObject(scope);
+    m_expression = QString::fromUtf8(expression);
+    m_expressionFunctionValid = false;
+    m_expressionFunctionRewritten = isRewritten;
+    m_fileName = fileName;
+    m_line = line;
+    m_column = column;
+}
+
+QQmlBoundSignalExpression::QQmlBoundSignalExpression(QQmlContextData *ctxt, QObject *scope, const QString &expression,
+                                                     bool isRewritten, const QString &fileName, int line, int column)
+    : QQmlJavaScriptExpression(&QQmlBoundSignalExpression_jsvtable)
+{
+    setNotifyOnValueChanged(false);
+    setContext(ctxt);
+    setScopeObject(scope);
+    m_expression = expression;
+    m_expressionFunctionValid = false;
+    m_expressionFunctionRewritten = isRewritten;
+    m_fileName = fileName;
+    m_line = line;
+    m_column = column;
+}
+
+QQmlBoundSignalExpression::~QQmlBoundSignalExpression()
+{
+    qPersistentDispose(m_v8function);
+    qPersistentDispose(m_v8qmlscope);
+}
+
+QString QQmlBoundSignalExpression::expressionIdentifier(QQmlJavaScriptExpression *e)
+{
+    QQmlBoundSignalExpression *This = static_cast<QQmlBoundSignalExpression *>(e);
+    return QLatin1String("\"") + This->m_expression + QLatin1String("\"");
+}
+
+void QQmlBoundSignalExpression::expressionChanged(QQmlJavaScriptExpression *)
+{
+    // bound signals do not notify on change.
+}
+
+// This mirrors code in QQmlExpressionPrivate::value() and v8value().
+// Any change made here should be made there and vice versa.
+void QQmlBoundSignalExpression::evaluate(QObject *secondaryScope)
+{
+    Q_ASSERT (context() && engine());
+    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine());
+
+    ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.
+    {
+        v8::HandleScope handle_scope;
+        v8::Context::Scope context_scope(ep->v8engine()->context());
+        if (!m_expressionFunctionValid) {
+            bool ok = true;
+            QString code;
+            if (m_expressionFunctionRewritten) {
+                code = m_expression;
+            } else {
+                QQmlRewrite::RewriteSignalHandler rewriteSignalHandler;
+                code = rewriteSignalHandler(m_expression, m_functionName, &ok);
+            }
+
+            if (ok)
+                m_v8function = evalFunction(context(), scopeObject(), code, m_fileName, m_line, &m_v8qmlscope);
+
+            if (m_v8function.IsEmpty() || m_v8function->IsNull()) {
+                ep->dereferenceScarceResources();
+                return; // could not evaluate function.  Not valid.
+            }
+
+            setUseSharedContext(false);
+            m_expressionFunctionValid = true;
+        }
+
+        if (secondaryScope) {
+            QObject *restoreSecondaryScope = 0;
+            restoreSecondaryScope = ep->v8engine()->contextWrapper()->setSecondaryScope(m_v8qmlscope, secondaryScope);
+            QQmlJavaScriptExpression::evaluate(context(), m_v8function, 0);
+            ep->v8engine()->contextWrapper()->setSecondaryScope(m_v8qmlscope, restoreSecondaryScope);
+        } else {
+            QQmlJavaScriptExpression::evaluate(context(), m_v8function, 0);
+        }
+    }
+    ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.
+}
+
+////////////////////////////////////////////////////////////////////////
+
 class QQmlBoundSignalParameters : public QObject
 {
 Q_OBJECT
@@ -144,7 +244,7 @@ int QQmlBoundSignal::index() const
 /*!
     Returns the signal expression.
 */
-QQmlExpression *QQmlBoundSignal::expression() const
+QQmlBoundSignalExpression *QQmlBoundSignal::expression() const
 {
     return m_expression;
 }
@@ -156,9 +256,9 @@ QQmlExpression *QQmlBoundSignal::expression() const
     The QQmlBoundSignal instance takes ownership of \a e.  The caller is 
     assumes ownership of the returned QQmlExpression.
 */
-QQmlExpression *QQmlBoundSignal::setExpression(QQmlExpression *e)
+QQmlBoundSignalExpression *QQmlBoundSignal::setExpression(QQmlBoundSignalExpression *e)
 {
-    QQmlExpression *rv = m_expression;
+    QQmlBoundSignalExpression *rv = m_expression;
     m_expression = e;
     if (m_expression) m_expression->setNotifyOnValueChanged(false);
     return rv;
@@ -183,8 +283,8 @@ int QQmlBoundSignal::qt_metacall(QMetaObject::Call c, int id, void **a)
         }
 
         if (m_params) m_params->setValues(a);
-        if (m_expression && m_expression->engine()) {
-            QQmlExpressionPrivate::get(m_expression)->value(m_params);
+        if (m_expression && m_expression->context() && m_expression->engine()) {
+            m_expression->evaluate(m_params);
             if (m_expression && m_expression->hasError())
                 QQmlEnginePrivate::warning(m_expression->engine(), m_expression->error());
         }
@@ -324,7 +424,7 @@ int QQmlBoundSignalNoParams::index() const
 /*!
     Returns the signal expression.
 */
-QQmlExpression *QQmlBoundSignalNoParams::expression() const
+QQmlBoundSignalExpression *QQmlBoundSignalNoParams::expression() const
 {
     return m_expression;
 }
@@ -336,9 +436,9 @@ QQmlExpression *QQmlBoundSignalNoParams::expression() const
     The QQmlBoundSignalNoParams instance takes ownership of \a e.  The caller is
     assumes ownership of the returned QQmlExpression.
 */
-QQmlExpression *QQmlBoundSignalNoParams::setExpression(QQmlExpression *e)
+QQmlBoundSignalExpression *QQmlBoundSignalNoParams::setExpression(QQmlBoundSignalExpression *e)
 {
-    QQmlExpression *rv = m_expression;
+    QQmlBoundSignalExpression *rv = m_expression;
     m_expression = e;
     if (m_expression) m_expression->setNotifyOnValueChanged(false);
     return rv;
@@ -356,9 +456,8 @@ void QQmlBoundSignalNoParams::subscriptionCallback(QQmlNotifierEndpoint *e)
     QQmlHandlingSignalProfiler prof(s->m_owner, s->m_index, s->m_expression);
 
     s->m_isEvaluating = true;
-
     if (s->m_expression && s->m_expression->engine()) {
-        QQmlExpressionPrivate::get(s->m_expression)->value();
+        s->m_expression->evaluate(); // evaluate signal expression.
         if (s->m_expression && s->m_expression->hasError())
             QQmlEnginePrivate::warning(s->m_expression->engine(), s->m_expression->error());
     }
diff --git a/src/qml/qml/qqmlboundsignal_p.h b/src/qml/qml/qqmlboundsignal_p.h
index 5fc8c3522f..22cc5a9f83 100644
--- a/src/qml/qml/qqmlboundsignal_p.h
+++ b/src/qml/qml/qqmlboundsignal_p.h
@@ -53,15 +53,52 @@
 // We mean it.
 //
 
-#include "qqmlexpression.h"
-
 #include <QtCore/qmetaobject.h>
 
+#include <private/qqmlabstractexpression_p.h>
+#include <private/qqmljavascriptexpression_p.h>
 #include <private/qqmlnotifier_p.h>
 #include <private/qobject_p.h>
 
 QT_BEGIN_NAMESPACE
 
+class Q_QML_PRIVATE_EXPORT QQmlBoundSignalExpression : public QQmlAbstractExpression, public QQmlJavaScriptExpression
+{
+public:
+    QQmlBoundSignalExpression(QQmlContextData *ctxt, QObject *scope, const QByteArray &expression,
+                              bool isRewritten, const QString &fileName, int line, int column);
+    QQmlBoundSignalExpression(QQmlContextData *ctxt, QObject *scope, const QString &expression,
+                              bool isRewritten, const QString &fileName, int line, int column);
+    ~QQmlBoundSignalExpression();
+
+    // "inherited" from QQmlJavaScriptExpression.
+    static QString expressionIdentifier(QQmlJavaScriptExpression *);
+    static void expressionChanged(QQmlJavaScriptExpression *);
+
+    // evaluation of a bound signal expression doesn't return any value
+    void evaluate(QObject *secondaryScope = 0);
+
+    QString sourceFile() const { return m_fileName; }
+    int lineNumber() const { return m_line; }
+    int columnNumber() const { return m_column; }
+    QString expression() const { return m_expression; }
+
+    QQmlEngine *engine() const { return context() ? context()->engine : 0; }
+
+private:
+    v8::Persistent<v8::Object> m_v8qmlscope;
+    v8::Persistent<v8::Function> m_v8function;
+
+    QString m_expression;
+    QString m_functionName; // hint for debugger
+    QString m_fileName;
+    int m_line;
+    int m_column;
+
+    bool m_expressionFunctionValid:1;
+    bool m_expressionFunctionRewritten:1;
+};
+
 class Q_QML_EXPORT QQmlAbstractBoundSignal
 {
 public:
@@ -69,8 +106,8 @@ public:
     virtual ~QQmlAbstractBoundSignal();
 
     virtual int index() const = 0;
-    virtual QQmlExpression *expression() const = 0;
-    virtual QQmlExpression *setExpression(QQmlExpression *) = 0;
+    virtual QQmlBoundSignalExpression *expression() const = 0;
+    virtual QQmlBoundSignalExpression *setExpression(QQmlBoundSignalExpression *) = 0;
     virtual QObject *object() = 0;
 
     void addToObject();
@@ -93,8 +130,8 @@ public:
 
     int index() const;
 
-    QQmlExpression *expression() const;
-    QQmlExpression *setExpression(QQmlExpression *);
+    QQmlBoundSignalExpression *expression() const;
+    QQmlBoundSignalExpression *setExpression(QQmlBoundSignalExpression *);
     QObject *object() { return m_owner; }
 
     bool isEvaluating() const { return m_isEvaluating; }
@@ -103,7 +140,7 @@ protected:
     virtual int qt_metacall(QMetaObject::Call c, int id, void **a);
 
 private:
-    QQmlExpression *m_expression;
+    QQmlBoundSignalExpression *m_expression;
     QMetaMethod m_signal;
     bool m_paramsValid : 1;
     bool m_isEvaluating : 1;
@@ -120,8 +157,8 @@ public:
 
     int index() const;
 
-    QQmlExpression *expression() const;
-    QQmlExpression *setExpression(QQmlExpression *);
+    QQmlBoundSignalExpression *expression() const;
+    QQmlBoundSignalExpression *setExpression(QQmlBoundSignalExpression *);
     QObject *object() { return m_owner; }
 
     static void subscriptionCallback(QQmlNotifierEndpoint *e);
@@ -129,7 +166,7 @@ public:
     bool isEvaluating() const { return m_isEvaluating; }
 
 private:
-    QQmlExpression *m_expression;
+    QQmlBoundSignalExpression *m_expression;
     QObject *m_owner;
     int m_index;
     bool m_isEvaluating;
diff --git a/src/qml/qml/qqmlexpression.cpp b/src/qml/qml/qqmlexpression.cpp
index d760486605..6e20047cf0 100644
--- a/src/qml/qml/qqmlexpression.cpp
+++ b/src/qml/qml/qqmlexpression.cpp
@@ -351,7 +351,7 @@ void QQmlExpression::setExpression(const QString &expression)
 }
 
 // Must be called with a valid handle scope
-v8::Local<v8::Value> QQmlExpressionPrivate::v8value(QObject *secondaryScope, bool *isUndefined)
+v8::Local<v8::Value> QQmlExpressionPrivate::v8value(bool *isUndefined)
 {
     if (!expressionFunctionValid) {
         bool ok = true;
@@ -369,21 +369,10 @@ v8::Local<v8::Value> QQmlExpressionPrivate::v8value(QObject *secondaryScope, boo
         expressionFunctionValid = true;
     }
 
-
-    if (secondaryScope) {
-        v8::Local<v8::Value> result;
-        QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
-        QObject *restoreSecondaryScope = 0;
-        restoreSecondaryScope = ep->v8engine()->contextWrapper()->setSecondaryScope(v8qmlscope, secondaryScope);
-        result = evaluate(context(), v8function, isUndefined);
-        ep->v8engine()->contextWrapper()->setSecondaryScope(v8qmlscope, restoreSecondaryScope);
-        return result;
-    } else {
-        return evaluate(context(), v8function, isUndefined);
-    }
+    return evaluate(context(), v8function, isUndefined);
 }
 
-QVariant QQmlExpressionPrivate::value(QObject *secondaryScope, bool *isUndefined)
+QVariant QQmlExpressionPrivate::value(bool *isUndefined)
 {
     Q_Q(QQmlExpression);
 
@@ -400,7 +389,7 @@ QVariant QQmlExpressionPrivate::value(QObject *secondaryScope, bool *isUndefined
     {
         v8::HandleScope handle_scope;
         v8::Context::Scope context_scope(ep->v8engine()->context());
-        v8::Local<v8::Value> result = v8value(secondaryScope, isUndefined);
+        v8::Local<v8::Value> result = v8value(isUndefined);
         rv = ep->v8engine()->toVariant(result, qMetaTypeId<QList<QObject*> >());
     }
 
@@ -421,7 +410,7 @@ QVariant QQmlExpressionPrivate::value(QObject *secondaryScope, bool *isUndefined
 QVariant QQmlExpression::evaluate(bool *valueIsUndefined)
 {
     Q_D(QQmlExpression);
-    return d->value(0, valueIsUndefined);
+    return d->value(valueIsUndefined);
 }
 
 /*!
diff --git a/src/qml/qml/qqmlexpression_p.h b/src/qml/qml/qqmlexpression_p.h
index 186e3aebf9..d3d27f259d 100644
--- a/src/qml/qml/qqmlexpression_p.h
+++ b/src/qml/qml/qqmlexpression_p.h
@@ -82,9 +82,9 @@ public:
     void init(QQmlContextData *, const QString &, bool, QObject *, const QString &, int, int);
     void init(QQmlContextData *, const QByteArray &, bool, QObject *, const QString &, int, int);
 
-    QVariant value(QObject *secondaryScope = 0, bool *isUndefined = 0);
+    QVariant value(bool *isUndefined = 0);
 
-    v8::Local<v8::Value> v8value(QObject *secondaryScope = 0, bool *isUndefined = 0);
+    v8::Local<v8::Value> v8value(bool *isUndefined = 0);
 
     static inline QQmlExpressionPrivate *get(QQmlExpression *expr);
     static inline QQmlExpression *get(QQmlExpressionPrivate *expr);
diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index b798215fa5..1b01a7d7c1 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -920,7 +920,7 @@ QQmlPropertyPrivate::setBindingNoEnable(QObject *object, int coreIndex, int valu
     Returns the expression associated with this signal property, or 0 if no 
     signal expression exists.
 */
-QQmlExpression *
+QQmlBoundSignalExpression *
 QQmlPropertyPrivate::signalExpression(const QQmlProperty &that)
 {
     if (!(that.type() & QQmlProperty::SignalProperty))
@@ -948,9 +948,9 @@ QQmlPropertyPrivate::signalExpression(const QQmlProperty &that)
     Ownership of \a expr transfers to QML.  Ownership of the return value is
     assumed by the caller.
 */
-QQmlExpression *
+QQmlBoundSignalExpression *
 QQmlPropertyPrivate::setSignalExpression(const QQmlProperty &that,
-                                                     QQmlExpression *expr) 
+                                         QQmlBoundSignalExpression *expr)
 {
     if (!(that.type() & QQmlProperty::SignalProperty)) {
         delete expr;
@@ -975,7 +975,7 @@ QQmlPropertyPrivate::setSignalExpression(const QQmlProperty &that,
             signal = new QQmlBoundSignal(that.d->object, that.method(), that.d->object);
         else
             signal = new QQmlBoundSignalNoParams(that.d->object, that.method(), that.d->object);
-        QQmlExpression *oldExpr = signal->setExpression(expr);
+        QQmlBoundSignalExpression *oldExpr = signal->setExpression(expr);
         signal->addToObject();
         return oldExpr;
     } else {
diff --git a/src/qml/qml/qqmlproperty_p.h b/src/qml/qml/qqmlproperty_p.h
index f4a9ced53b..e33c95ae41 100644
--- a/src/qml/qml/qqmlproperty_p.h
+++ b/src/qml/qml/qqmlproperty_p.h
@@ -64,7 +64,7 @@
 QT_BEGIN_NAMESPACE
 
 class QQmlContext;
-class QQmlExpression;
+class QQmlBoundSignalExpression;
 class QQmlEnginePrivate;
 class QQmlJavaScriptExpression;
 class Q_QML_PRIVATE_EXPORT QQmlPropertyPrivate : public QQmlRefCount
@@ -140,9 +140,9 @@ public:
     static QQmlAbstractBinding *setBinding(const QQmlProperty &that,
                                                    QQmlAbstractBinding *,
                                                    WriteFlags flags = DontRemoveBinding);
-    static QQmlExpression *signalExpression(const QQmlProperty &that);
-    static QQmlExpression *setSignalExpression(const QQmlProperty &that, 
-                                                       QQmlExpression *) ;
+    static QQmlBoundSignalExpression *signalExpression(const QQmlProperty &that);
+    static QQmlBoundSignalExpression *setSignalExpression(const QQmlProperty &that,
+                                                          QQmlBoundSignalExpression *) ;
     static bool write(const QQmlProperty &that, const QVariant &, WriteFlags);
     static bool writeBinding(QObject *, const QQmlPropertyData &,
                              QQmlContextData *context,
diff --git a/src/qml/qml/qqmlrewrite.cpp b/src/qml/qml/qqmlrewrite.cpp
index 72bd23955b..0bd8597ec4 100644
--- a/src/qml/qml/qqmlrewrite.cpp
+++ b/src/qml/qml/qqmlrewrite.cpp
@@ -419,6 +419,21 @@ QString RewriteSignalHandler::operator()(QQmlJS::AST::Node *node, const QString
     return rewritten;
 }
 
+QString RewriteSignalHandler::operator()(const QString &code, const QString &name, bool *ok)
+{
+    Engine engine;
+    Lexer lexer(&engine);
+    Parser parser(&engine);
+    lexer.setCode(code, 0);
+    parser.parseStatement();
+    if (!parser.statement()) {
+        if (ok) *ok = false;
+        return QString();
+    }
+    if (ok) *ok = true;
+    return operator()(parser.statement(), code, name);
+}
+
 } // namespace QQmlRewrite
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmlrewrite_p.h b/src/qml/qml/qqmlrewrite_p.h
index 1d69839878..73ff50a040 100644
--- a/src/qml/qml/qqmlrewrite_p.h
+++ b/src/qml/qml/qqmlrewrite_p.h
@@ -133,6 +133,7 @@ class RewriteSignalHandler: protected AST::Visitor
 public:
     RewriteSignalHandler();
     QString operator()(QQmlJS::AST::Node *node, const QString &code, const QString &name);
+    QString operator()(const QString &code, const QString &name, bool *ok = 0);
 
 protected:
     void rewriteMultilineStrings(QString &code);
diff --git a/src/qml/qml/qqmlvme.cpp b/src/qml/qml/qqmlvme.cpp
index 6010adfcfc..5a9fa40771 100644
--- a/src/qml/qml/qqmlvme.cpp
+++ b/src/qml/qml/qqmlvme.cpp
@@ -716,8 +716,8 @@ QObject *QQmlVME::run(QList<QQmlError> *errors,
                 bs = new QQmlBoundSignal(target, signal, target);
             else
                 bs = new QQmlBoundSignalNoParams(target, signal, target);
-            QQmlExpression *expr =
-                new QQmlExpression(CTXT, context, DATAS.at(instr.value), true, COMP->name, instr.line, instr.column, *new QQmlExpressionPrivate);
+            QQmlBoundSignalExpression *expr =
+                new QQmlBoundSignalExpression(CTXT, context, DATAS.at(instr.value), true, COMP->name, instr.line, instr.column);
             bs->setExpression(expr);
             bs->addToObject();
         QML_END_INSTR(StoreSignal)
diff --git a/src/quick/util/qquickconnections.cpp b/src/quick/util/qquickconnections.cpp
index acc9738f2c..2ba34a24c3 100644
--- a/src/quick/util/qquickconnections.cpp
+++ b/src/quick/util/qquickconnections.cpp
@@ -280,8 +280,8 @@ void QQuickConnections::connectSignals()
                     location = ddata->outerContext->urlString;
             }
 
-            QQmlExpression *expression = ctxtdata ?
-                QQmlExpressionPrivate::create(ctxtdata, 0, script, true, location, line, column) : 0;
+            QQmlBoundSignalExpression *expression = ctxtdata ?
+                new QQmlBoundSignalExpression(ctxtdata, 0, script, true, location, line, column) : 0;
             signal->setExpression(expression);
             signal->addToObject();
             d->boundsignals += signal;
diff --git a/src/quick/util/qquickpropertychanges.cpp b/src/quick/util/qquickpropertychanges.cpp
index 8b0818c96c..4bff006d9b 100644
--- a/src/quick/util/qquickpropertychanges.cpp
+++ b/src/quick/util/qquickpropertychanges.cpp
@@ -55,6 +55,7 @@
 #include <private/qqmlproperty_p.h>
 #include <private/qqmlcontext_p.h>
 #include <private/qquickstate_p_p.h>
+#include <private/qqmlboundsignal_p.h>
 
 #include <QtCore/qdebug.h>
 
@@ -139,7 +140,7 @@ class QQuickReplaceSignalHandler : public QQuickActionEvent
 {
 public:
     QQuickReplaceSignalHandler() : expression(0), reverseExpression(0),
-                                rewindExpression(0), ownedExpression(0) {}
+                                rewindExpression(0), ownedExpression(0), ownedExpressionWatcher(0) {}
     ~QQuickReplaceSignalHandler() {
         delete ownedExpression;
     }
@@ -147,22 +148,35 @@ public:
     virtual EventType type() const { return SignalHandler; }
 
     QQmlProperty property;
-    QQmlExpression *expression;
-    QQmlExpression *reverseExpression;
-    QQmlExpression *rewindExpression;
-    QQmlGuard<QQmlExpression> ownedExpression;
+    QQmlBoundSignalExpression *expression;
+    QQmlBoundSignalExpression *reverseExpression;
+    QQmlBoundSignalExpression *rewindExpression;
+    QQmlBoundSignalExpression *ownedExpression;
+    QQmlAbstractExpression::DeleteWatcher *ownedExpressionWatcher; // TODO: refactor the ownership impl.
 
     virtual void execute(Reason) {
         ownedExpression = QQmlPropertyPrivate::setSignalExpression(property, expression);
-        if (ownedExpression == expression)
+        if (ownedExpression == expression) {
+            delete ownedExpressionWatcher;
+            ownedExpressionWatcher = 0;
             ownedExpression = 0;
+        } else if (ownedExpression) {
+            delete ownedExpressionWatcher;
+            ownedExpressionWatcher = new QQmlAbstractExpression::DeleteWatcher(ownedExpression);
+        }
     }
 
     virtual bool isReversable() { return true; }
     virtual void reverse(Reason) {
         ownedExpression = QQmlPropertyPrivate::setSignalExpression(property, reverseExpression);
-        if (ownedExpression == reverseExpression)
+        if (ownedExpression == reverseExpression) {
+            delete ownedExpressionWatcher;
+            ownedExpressionWatcher = 0;
             ownedExpression = 0;
+        } else if (ownedExpression) {
+            delete ownedExpressionWatcher;
+            ownedExpressionWatcher = new QQmlAbstractExpression::DeleteWatcher(ownedExpression);
+        }
     }
 
     virtual void saveOriginals() {
@@ -181,6 +195,8 @@ public:
         if (rsh->ownedExpression == reverseExpression) {
             ownedExpression = rsh->ownedExpression;
             rsh->ownedExpression = 0;
+            delete ownedExpressionWatcher;
+            ownedExpressionWatcher = new QQmlAbstractExpression::DeleteWatcher(ownedExpression);
         }
     }
 
@@ -225,11 +241,17 @@ public:
     public:
         ExpressionChange(const QString &_name,
                          QQmlBinding::Identifier _id,
-                         QQmlExpression *_expr)
-            : name(_name), id(_id), expression(_expr) {}
+                         const QString& _expr,
+                         const QUrl &_url,
+                         int _line,
+                         int _column)
+            : name(_name), id(_id), expression(_expr), url(_url), line(_line), column(_column) {}
         QString name;
         QQmlBinding::Identifier id;
-        QQmlExpression *expression;
+        QString expression;
+        QUrl url;
+        int line;
+        int column;
     };
 
     QList<QPair<QString, QVariant> > properties;
@@ -334,20 +356,36 @@ void QQuickPropertyChangesPrivate::decode()
 
         QQmlProperty prop = property(name);      //### better way to check for signal property?
         if (prop.type() & QQmlProperty::SignalProperty) {
-            QQmlExpression *expression = new QQmlExpression(qmlContext(q), object, data.toString());
+            QString expression = data.toString();
+            QUrl url = QUrl();
+            int line = -1;
+            int column = -1;
+
             QQmlData *ddata = QQmlData::get(q);
-            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty())
-                expression->setSourceLocation(ddata->outerContext->url.toString(), ddata->lineNumber, ddata->columnNumber);
+            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty()) {
+                url = ddata->outerContext->url;
+                line = ddata->lineNumber;
+                column = ddata->columnNumber;
+            }
+
             QQuickReplaceSignalHandler *handler = new QQuickReplaceSignalHandler;
             handler->property = prop;
-            handler->expression = expression;
+            handler->expression = new QQmlBoundSignalExpression(QQmlContextData::get(qmlContext(q)), object, expression, false, url.toString(), line, column);
             signalReplacements << handler;
-        } else if (isScript) {
-            QQmlExpression *expression = new QQmlExpression(qmlContext(q), object, data.toString());
+        } else if (isScript) { // binding
+            QString expression = data.toString();
+            QUrl url = QUrl();
+            int line = -1;
+            int column = -1;
+
             QQmlData *ddata = QQmlData::get(q);
-            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty())
-                expression->setSourceLocation(ddata->outerContext->url.toString(), ddata->lineNumber, ddata->columnNumber);
-            expressions << ExpressionChange(name, id, expression);
+            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty()) {
+                url = ddata->outerContext->url;
+                line = ddata->lineNumber;
+                column = ddata->columnNumber;
+            }
+
+            expressions << ExpressionChange(name, id, expression, url, line, column);
         } else {
             properties << qMakePair(name, data);
         }
@@ -374,8 +412,6 @@ QQuickPropertyChanges::QQuickPropertyChanges()
 QQuickPropertyChanges::~QQuickPropertyChanges()
 {
     Q_D(QQuickPropertyChanges);
-    for(int ii = 0; ii < d->expressions.count(); ++ii)
-        delete d->expressions.at(ii).expression;
     for(int ii = 0; ii < d->signalReplacements.count(); ++ii)
         delete d->signalReplacements.at(ii);
 }
@@ -460,7 +496,8 @@ QQuickPropertyChanges::ActionList QQuickPropertyChanges::actions()
 
     for (int ii = 0; ii < d->expressions.count(); ++ii) {
 
-        const QString &property = d->expressions.at(ii).name;
+        QQuickPropertyChangesPrivate::ExpressionChange e = d->expressions.at(ii);
+        const QString &property = e.name;
         QQmlProperty prop = d->property(property);
 
         if (prop.isValid()) {
@@ -471,16 +508,18 @@ QQuickPropertyChanges::ActionList QQuickPropertyChanges::actions()
             a.specifiedObject = d->object;
             a.specifiedProperty = property;
 
+            QQmlBinding *newBinding = e.id != QQmlBinding::Invalid ? QQmlBinding::createBinding(e.id, object(), qmlContext(this), e.url.toString(), e.column) : 0;
+            if (!newBinding)
+                newBinding = new QQmlBinding(e.expression, false, object(), QQmlContextData::get(qmlContext(this)), e.url.toString(), e.line, e.column);
+
             if (d->isExplicit) {
-                a.toValue = d->expressions.at(ii).expression->evaluate();
+                // in this case, we don't want to assign a binding, per se,
+                // so we evaluate the expression and assign the result.
+                // XXX TODO: add a static QQmlJavaScriptExpression::evaluate(QString)
+                // so that we can avoid creating then destroying the binding in this case.
+                a.toValue = newBinding->evaluate();
+                newBinding->destroy();
             } else {
-                QQmlExpression *e = d->expressions.at(ii).expression;
-
-                QQmlBinding::Identifier id = d->expressions.at(ii).id;
-                QQmlBinding *newBinding = id != QQmlBinding::Invalid ? QQmlBinding::createBinding(id, object(), qmlContext(this), e->sourceFile(), e->lineNumber()) : 0;
-                if (!newBinding)
-                    newBinding = new QQmlBinding(e->expression(), false, object(), QQmlContextData::get(qmlContext(this)),
-                                                 e->sourceFile(), e->lineNumber(), e->columnNumber());
                 newBinding->setTarget(prop);
                 a.toBinding = QQmlAbstractBinding::getPointer(newBinding);
                 a.deletableToBinding = true;
@@ -635,14 +674,14 @@ void QQuickPropertyChanges::changeExpression(const QString &name, const QString
 
     QMutableListIterator<ExpressionEntry> expressionIterator(d->expressions);
     while (expressionIterator.hasNext()) {
-        const ExpressionEntry &entry = expressionIterator.next();
+        ExpressionEntry &entry = expressionIterator.next();
         if (entry.name == name) {
-            entry.expression->setExpression(expression);
+            entry.expression = expression;
             if (state() && state()->isStateActive()) {
                 QQmlAbstractBinding *oldBinding = QQmlPropertyPrivate::binding(d->property(name));
                 if (oldBinding) {
-                       QQmlPropertyPrivate::setBinding(d->property(name), 0);
-                       oldBinding->destroy();
+                   QQmlPropertyPrivate::setBinding(d->property(name), 0);
+                   oldBinding->destroy();
                 }
 
                 QQmlBinding *newBinding = new QQmlBinding(expression, object(), qmlContext(this));
@@ -653,8 +692,8 @@ void QQuickPropertyChanges::changeExpression(const QString &name, const QString
         }
     }
 
-    QQmlExpression *newExpression = new QQmlExpression(qmlContext(this), d->object, expression);
-    expressionIterator.insert(ExpressionEntry(name, QQmlBinding::Invalid, newExpression));
+    // adding a new expression.
+    expressionIterator.insert(ExpressionEntry(name, QQmlBinding::Invalid, expression, QUrl(), -1, -1));
 
     if (state() && state()->isStateActive()) {
         if (hadValue) {
@@ -675,11 +714,14 @@ void QQuickPropertyChanges::changeExpression(const QString &name, const QString
             action.specifiedObject = object();
             action.specifiedProperty = name;
 
-
+            QQmlBinding *newBinding = new QQmlBinding(expression, object(), qmlContext(this));
             if (d->isExplicit) {
-                action.toValue = newExpression->evaluate();
+                // don't assign the binding, merely evaluate the expression.
+                // XXX TODO: add a static QQmlJavaScriptExpression::evaluate(QString)
+                // so that we can avoid creating then destroying the binding in this case.
+                action.toValue = newBinding->evaluate();
+                newBinding->destroy();
             } else {
-                QQmlBinding *newBinding = new QQmlBinding(newExpression->expression(), object(), qmlContext(this));
                 newBinding->setTarget(d->property(name));
                 action.toBinding = QQmlAbstractBinding::getPointer(newBinding);
                 action.deletableToBinding = true;
@@ -714,7 +756,7 @@ QVariant QQuickPropertyChanges::property(const QString &name) const
     while (expressionIterator.hasNext()) {
         const ExpressionEntry &entry = expressionIterator.next();
         if (entry.name == name) {
-            return QVariant(entry.expression->expression());
+            return QVariant(entry.expression);
         }
     }
 
@@ -773,7 +815,7 @@ QString QQuickPropertyChanges::expression(const QString &name) const
     while (expressionIterator.hasNext()) {
         const ExpressionEntry &entry = expressionIterator.next();
         if (entry.name == name) {
-            return entry.expression->expression();
+            return entry.expression;
         }
     }
 
diff --git a/tests/auto/qml/debugger/qqmlenginedebugservice/tst_qqmlenginedebugservice.cpp b/tests/auto/qml/debugger/qqmlenginedebugservice/tst_qqmlenginedebugservice.cpp
index b66ba289ce..d99b4e6066 100644
--- a/tests/auto/qml/debugger/qqmlenginedebugservice/tst_qqmlenginedebugservice.cpp
+++ b/tests/auto/qml/debugger/qqmlenginedebugservice/tst_qqmlenginedebugservice.cpp
@@ -205,7 +205,7 @@ void tst_QQmlEngineDebugService::recursiveObjectTest(
         // signal properties are fake - they are generated from QQmlAbstractBoundSignal children
         if (p.name.startsWith("on") && p.name.length() > 2 && p.name[2].isUpper()) {
             QString signal = p.value.toString();
-            QQmlExpression *expr = QQmlPropertyPrivate::signalExpression(QQmlProperty(o, p.name));
+            QQmlBoundSignalExpression *expr = QQmlPropertyPrivate::signalExpression(QQmlProperty(o, p.name));
             QVERIFY(expr && expr->expression() == signal);
             QVERIFY(p.valueTypeName.isEmpty());
             QVERIFY(p.binding.isEmpty());
diff --git a/tests/auto/qml/qqmlproperty/tst_qqmlproperty.cpp b/tests/auto/qml/qqmlproperty/tst_qqmlproperty.cpp
index 2dde5f003d..23f7c3437d 100644
--- a/tests/auto/qml/qqmlproperty/tst_qqmlproperty.cpp
+++ b/tests/auto/qml/qqmlproperty/tst_qqmlproperty.cpp
@@ -45,6 +45,7 @@
 #include <QtQml/qqmlproperty.h>
 #include <QtQml/private/qqmlproperty_p.h>
 #include <private/qqmlbinding_p.h>
+#include <private/qqmlboundsignal_p.h>
 #include <QtWidgets/QLineEdit>
 #include <QtCore/qfileinfo.h>
 #include <QtCore/qdir.h>
@@ -146,8 +147,9 @@ void tst_qqmlproperty::qmlmetaproperty()
 
     QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
     QVERIFY(binding != 0);
-    QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-    QVERIFY(expression != 0);
+    QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+    QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+    QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
     QObject *obj = new QObject;
 
@@ -179,8 +181,8 @@ void tst_qqmlproperty::qmlmetaproperty()
     QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
     QVERIFY(binding == 0);
     QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-    QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-    QVERIFY(expression == 0);
+    QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+    QVERIFY(sigExprWatcher.wasDeleted());
     QCOMPARE(prop.index(), -1);
     QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -249,8 +251,9 @@ void tst_qqmlproperty::qmlmetaproperty_object()
 
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -282,8 +285,8 @@ void tst_qqmlproperty::qmlmetaproperty_object()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), -1);
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -296,8 +299,9 @@ void tst_qqmlproperty::qmlmetaproperty_object()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -331,8 +335,8 @@ void tst_qqmlproperty::qmlmetaproperty_object()
         QVERIFY(binding != 0);
         QVERIFY(QQmlPropertyPrivate::binding(prop) == binding.data());
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfProperty("defaultProperty"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -350,8 +354,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
 
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -383,8 +388,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), -1);
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -397,8 +402,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -432,8 +438,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QVERIFY(binding != 0);
         QVERIFY(QQmlPropertyPrivate::binding(prop) == binding.data());
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfProperty("defaultProperty"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -446,8 +452,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -479,9 +486,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression != 0);
-        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == expression.data());
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(!sigExprWatcher.wasDeleted());
+        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == sigExpr);
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfMethod("clicked()"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -494,8 +501,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -527,9 +535,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression != 0);
-        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == expression.data());
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(!sigExprWatcher.wasDeleted());
+        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == sigExpr);
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfMethod("oddlyNamedNotifySignal()"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -547,8 +555,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_context()
 
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -580,8 +589,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_context()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), -1);
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -594,8 +603,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_context()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -629,8 +639,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_context()
         QVERIFY(binding != 0);
         QVERIFY(QQmlPropertyPrivate::binding(prop) == binding.data());
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfProperty("defaultProperty"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -648,8 +658,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
 
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -681,8 +692,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), -1);
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -695,8 +706,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -730,8 +742,8 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QVERIFY(binding != 0);
         QVERIFY(QQmlPropertyPrivate::binding(prop) == binding.data());
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression == 0);
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(sigExprWatcher.wasDeleted());
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfProperty("defaultProperty"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -744,8 +756,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -777,9 +790,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression != 0);
-        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == expression.data());
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(!sigExprWatcher.wasDeleted());
+        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == sigExpr);
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfMethod("clicked()"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -792,8 +805,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QWeakPointer<QQmlAbstractBinding> binding(QQmlAbstractBinding::getPointer(new QQmlBinding(QLatin1String("null"), 0, engine.rootContext())));
         static_cast<QQmlBinding *>(binding.data())->setTarget(prop);
         QVERIFY(binding != 0);
-        QWeakPointer<QQmlExpression> expression(new QQmlExpression());
-        QVERIFY(expression != 0);
+        QQmlBoundSignalExpression *sigExpr = new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1);
+        QQmlAbstractExpression::DeleteWatcher sigExprWatcher(sigExpr);
+        QVERIFY(sigExpr != 0 && !sigExprWatcher.wasDeleted());
 
         QObject *obj = new QObject;
 
@@ -825,9 +839,9 @@ void tst_qqmlproperty::qmlmetaproperty_object_string_context()
         QVERIFY(QQmlPropertyPrivate::setBinding(prop, binding.data()) == 0);
         QVERIFY(binding == 0);
         QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == 0);
-        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, expression.data()) == 0);
-        QVERIFY(expression != 0);
-        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == expression.data());
+        QVERIFY(QQmlPropertyPrivate::setSignalExpression(prop, sigExpr) == 0);
+        QVERIFY(!sigExprWatcher.wasDeleted());
+        QVERIFY(QQmlPropertyPrivate::signalExpression(prop) == sigExpr);
         QCOMPARE(prop.index(), dobject.metaObject()->indexOfMethod("oddlyNamedNotifySignal()"));
         QCOMPARE(QQmlPropertyPrivate::valueTypeCoreIndex(prop), -1);
 
@@ -973,7 +987,7 @@ void tst_qqmlproperty::read()
         QQmlProperty p(&o, "onClicked");
         QCOMPARE(p.read(), QVariant());
 
-        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlExpression()));
+        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1)));
         QVERIFY(0 != QQmlPropertyPrivate::signalExpression(p));
 
         QCOMPARE(p.read(), QVariant());
@@ -985,7 +999,7 @@ void tst_qqmlproperty::read()
         QQmlProperty p(&o, "onPropertyWithNotifyChanged");
         QCOMPARE(p.read(), QVariant());
 
-        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlExpression()));
+        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1)));
         QVERIFY(0 != QQmlPropertyPrivate::signalExpression(p));
 
         QCOMPARE(p.read(), QVariant());
@@ -1141,7 +1155,7 @@ void tst_qqmlproperty::write()
         QQmlProperty p(&o, "onClicked");
         QCOMPARE(p.write(QVariant("console.log(1921)")), false);
 
-        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlExpression()));
+        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1)));
         QVERIFY(0 != QQmlPropertyPrivate::signalExpression(p));
 
         QCOMPARE(p.write(QVariant("console.log(1921)")), false);
@@ -1155,7 +1169,7 @@ void tst_qqmlproperty::write()
         QQmlProperty p(&o, "onPropertyWithNotifyChanged");
         QCOMPARE(p.write(QVariant("console.log(1921)")), false);
 
-        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlExpression()));
+        QVERIFY(0 == QQmlPropertyPrivate::setSignalExpression(p, new QQmlBoundSignalExpression(QQmlContextData::get(engine.rootContext()), 0, QLatin1String("null"), false, QString(), -1, -1)));
         QVERIFY(0 != QQmlPropertyPrivate::signalExpression(p));
 
         QCOMPARE(p.write(QVariant("console.log(1921)")), false);
diff --git a/tools/qmlprofiler/qmlprofiler.pro b/tools/qmlprofiler/qmlprofiler.pro
index b90554455f..7ab61e7a96 100644
--- a/tools/qmlprofiler/qmlprofiler.pro
+++ b/tools/qmlprofiler/qmlprofiler.pro
@@ -2,7 +2,7 @@ TEMPLATE = app
 TARGET   = qmlprofiler
 DESTDIR = $$QT.qml.bins
 
-QT += qml qml-private network core-private
+QT += qml qml-private v8-private network core-private
 
 target.path = $$[QT_INSTALL_BINS]
 INSTALLS += target